It is generally well known that the US auto fleet uses a higher proportion of gasoline to diesel as compared to most of the rest of the world. As a result, refineries in the US use hydrocrackers to produce naphtha which is a feedstock for other refining processes such as reforming to make gasoline or as gasoline blending stock. In other countries, particularly in Europe and Asia, hydrocrackers are designed and operated to produce diesel and less naphtha. The conditions and feedstock certainly have an impact on the product slate of a hydrocracker, but catalyst selection is probably the most influential driver of product slate.
To the extent that the US diesel market is, at times, oversupplied therefore driving down US diesel prices, excess diesel has often been exported. But, diesel demand in the U.S. has increased by approximately 40% since 1998 and is expected to continue increasing while gasoline demand has been commonly viewed as relatively flat, by comparison. As a result, refiners in North America have been and will be increasingly compelled to evaluate their processing options to expand diesel production. While it would be desirable to quickly alter the catalyst in a hydrocracker to thereby shift naphtha production to increase the net diesel production when prices are favorable, the cost of shutting down the hydrocracker and switch catalyst well exceeds any price opportunity almost regardless of the duration that favorable prices may exist. Indeed, it is most economical to run a hydrocracker as hydraulically full as practical for as long as it is productive before shutting down for a turn around and a new load of catalyst. The catalyst is typically spent at the end of a run. Such a time frame is usually measured in years and the diesel gasoline price advantage generally shifts seasonally to gasoline in the summer and to diesel in the winter.
What is needed is a more adjustable hydrocracker that is suited for producing higher volumes of naphtha and lower volumes of diesel when desired, such as during the summer gasoline production time producing less naphtha and more diesel in the winter or during a time that diesel has a higher profit margin than gasoline.